Glucosidase inhibitors: new approaches to malting efficiency

Lead Research Organisation: John Innes Centre
Department Name: Contracts Office

Abstract

Our aim is to enhance efficiency of the malting, brewing and distilling industries by exploiting new inhibitors of barley seed germination. In malting, the seedling accumulates starch-hydrolysing enzymes in the starch-storing endosperm. Seedling growth is then stopped by drying, and the malt is milled and mixed with hot water to allow the starch-hydrolysing enzymes to convert starch to sugars. These sugars are fermented by yeast to produce alcohol.
The goal of malting is to optimise accumulation of starch-hydrolysing enzymes while minimising starch degradation and rootlet growth in the seedling: these processes result in significant losses of fermentable material (5-10% of the grain dry weight).
We have discovered that rootlet growth and starch degradation are strongly inhibited by low concentrations of natural compounds including the iminosugar deoxynojirimycin. These natural compounds are thus potentially exciting new tools for reducing malting losses.
To exploit this discovery, we will use a library of naturally-occurring compounds to identify the most potent inhibitors of rootlet growth. Inhibitors will be applied to seeds undergoing micromalting. The impact on malting loss, malt quality, and food safety will be assessed and the commercial potential evaluated. In parallel we will use hypothesis-driven biochemical approaches to discover how iminosugars inhibit starch degradation in the endosperm. The gene(s) thus identified will be genetically mapped, and natural sequence variation assessed in a unique collection of elite barley cultivars to test, by association analysis, whether it plays a role in malting quality. This will require the collection to be phenotyped for relevant traits, including germination potential and cell wall modification and starch loss during germination. The information will reveal the potential importance of gene(s) we discover, and also permit a large-scale genome-wide genetic analysis of malting quality in elite barley germplasm.

Publications

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